SPACE/COSMOS
FAST discovers a rare millisecond pulsar with an extremely circular orbit
Pulsars are ultra-dense neutron stars left behind after massive stars explode. They spin at incredible speeds, emitting regular beams of electromagnetic radiation. When these beams sweep past Earth, astronomers detect periodic signals, much like flashes from a lighthouse.
Recently, China's Five-hundred-meter Aperture Spherical radio Telescope (FAST) — has discovered a new pulsar of significant research value, named PSR J1810−0623. This pulsar not only spins extremely fast, but its formation history also appears to record a long and complex "binary evolution story."
PSR J1810−0623 has a rotation period of just 4.55 milliseconds, meaning it spins about 220 times every second. Astronomers believe that the vast majority of millisecond pulsars are not born spinning this fast; rather, they are accelerated through long-term interactions with a companion star: material from the companion star falls onto the neutron star, transferring angular momentum and causing it to spin faster and faster. This process is known as "recycling." Through precise observations spanning six and a half years, the research team found that PSR J1810−0623 has undergone an extremely thorough recycling process. Not only is its rotation speed exceptionally high, but its surface magnetic field has also decayed to only about 100 million Gauss.
PSR J1810−0623 has a companion star, and the two orbit their common center of mass every 15.4 days. Based on observational calculations, this companion star has a mass of about 0.64 times that of the Sun and is likely a carbon-oxygen white dwarf. This clue reveals the origin of PSR J1810−0623: it was likely born in a "moderate-mass X-ray binary system". Over vast stretches of time, the companion star continuously transferred material to the neutron star, not only causing the latter to spin rapidly but also eventually depleting its own outer layers, leaving behind the white dwarf remnant we see today. This formation pathway is uncommon in the Milky Way, making such systems particularly valuable.
What particularly intrigues researchers is that the orbit of this binary system is nearly a perfect circle. The eccentricity of PSR J1810−0623's orbit is only about 0.000015, representing an orbit so close to circular that its elliptical shape is almost undetectable. Generally, long-term, stable mass transfer between binary stars gradually smooths out orbital irregularities, making the orbit increasingly circular. This characteristic is similar to a few known special systems, such as the famous PSR J1614−2230. However, the orbit of PSR J1810−0623 is even rounder, providing a new observational benchmark for testing binary evolution theories.
Beyond revealing binary evolution processes, this newly discovered pulsar can also help scientists study the Milky Way itself. The research team used the polarization properties of its radio signals to measure magnetic field information along the line of sight, thereby providing new data points for mapping the Galactic magnetic field structure.
In the future, as FAST and other radio telescopes continue long-term timing observations, scientists hope to further determine the true mass of this neutron star and even test gravitational theories through more precise orbital measurements. For studying pulsar recycling mechanisms, binary system evolution, and the structure of the Milky Way, PSR J1810−0623 will prove to be an immensely valuable "natural laboratory".
Journal
Science China Physics Mechanics and Astronomy
Method of Research
Observational study
TRACERS uses speedy electrons to trace solar energy’s path to Earth
First published results from Iowa-led NASA mission reveal new details of sun-Earth interaction
University of Iowa
image:
A University of Iowa-led research team has documented how energy from the sun interacts with Earth’s magnetic field and moves closer to our planet, using detailed electron measurements. In this image, speedy electrons act like messengers to convey information about those interactions, called magnetic reconnection, tens of thousands of miles from Earth’s surface.
view moreCredit: Jasper Halekas lab, University of Iowa
Physicists led by the University of Iowa have documented in the finest detail to date how energy from the sun interacts with Earth’s magnetic field, which could yield greater insights into solar effects on Earth that drive space weather.
In a new study, the researchers measured the velocities and concentrations of electrons in low-Earth orbit at locations called cusps, which act like conduits for charged particles from the sun to enter Earth’s ionosphere, the upper reaches of our planet’s atmosphere. Through those detailed measurements, the researchers were able to more precisely map the travel pattern of solar energy from magnetic reconnection — solar energy’s first encounter with Earth’s magnetic field tens of thousands of miles from Earth’s surface — to its interactions at cusps a few hundred miles above our planet.
“With magnetic reconnection, we don't really know how it varies at a fine scale. We have a hunch that it’s either varying in time or varying spatially,” says Jasper Halekas, professor in the Department of Physics and Astronomy at Iowa and the study’s corresponding author. “Our electron edge measurements reveal for the first time how these processes vary on small time and spatial scales at the edge of the cusp, helping us to better understand the efficiency of the sun-Earth coupling.”
The results come from TRACERS, the approximately $170 million mission funded by NASA and the largest external research award in University of Iowa history. Launched in July 2025, twin satellites swoop through low-Earth orbit, sampling electrons, ions, plasma, and other elements part of the interactions between the sun and the Earth.
“This is important because magnetic reconnection is how the energy from the sun gets into Earth’s system,” Halekas says. “It’s important to know the duty cycle of that reconnection — is it happening continuously, or is it sort of turning on and off?”
Electrons are key to better understanding magnetic reconnection events and how they reverberate closer to Earth. Because of their nearly nonexistent mass and high energies, think of them as ultra-speedy messengers, delivering the first news about magnetic reconnection some 30,000 miles away at the edges of Earth’s magnetic bubble and portending the ripple effects at cusps farther downstream in Earth’s ionosphere.
“The electrons are saying, magnetic reconnection is taking place way out here, and we’re letting you know that there’s going to be this wave of mass and energy coming to us,” Halekas explains.
The researchers cataloged 149 cusp encounters by one of the TRACERS spacecraft; 57 of those encounters showed characteristic electron dispersion signatures at the equatorward edge. The observations came from data collected by the Analyzer for Cusp Electrons instrument (ACE), designed and built at Iowa.
“The equatorward edge is the leading edge of the cusp, where the solar wind energy and plasma can first reach the ionosphere,” says Halekas, principal investigator for the ACE instrument. “The electron and ion signatures we see there are the proof we’re seeing the effects of magnetic reconnection.”
The study, “Electron dispersion at the electron edge of the Earth’s magnetospheric cusp,” was published online May 19 in the journal Geophysical Research Letters.
Contributing authors from Iowa are Sarah Henderson, Scott Bounds, Aidan Moore, Ivar Christopher, David Miles, Connor Feltman, George Hospodarsky, Allison Jaynes, Brendan Powers, and Shirsh Soni.
Other authors are Suranga Ruhunusiri and Karlheinz Trattner, from the University of Colorado-Boulder; John Bonnell and Marit Øieroset, from the University of California-Berkeley; Brandon Burkholder, from the University of Maryland-Baltimore County and NASA Goddard Space Flight Center; Iver Cairns, from the University of Sydney in Australia; Li-Jen Chen, Hyunju Connor, and John Dorelli, from NASA Goddard Space Flight Center; Ian DesJardin and Dibyendu Sur, from Catholic University of America and NASA Goddard Space Flight Center; Stephen Fuselier, from Southwest Research Institute and the University of Texas-San Antonio; Katherine Goodrich, from West Virginia University; James Labelle, from Dartmouth College; Steven Petrinec, from Lockheed Martin Advanced Technology Center, in Palo Alto, California; and Robert Strangeway, from the University of California-Los Angeles.
Journal
Geophysical Research Letters
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Electron Dispersion at the Electron Edge of the Earth's Magnetospheric Cusp
No comments:
Post a Comment